Controls for ventilation and exhaust ducts and fans

ABSTRACT

A ventilation or exhaust system, having ducting, and a fan assembly for placement in ducting of a ventilation or exhaust system for an environment space. The fan assembly has a motor having an output shaft, a fan mounted on the output shaft, and a brake mounted for operation on the motor. The brake is operable for stopping rotation of the motor upon a detection of a prescribed situation one or more of: the environmental space, and the ducting. Also included is a valve assembly having a valve member for placement in the ducting for movement between a first position where the ducting is substantially open, and a second position where the ducting is substantially closed. The valve member is adapted to move from the first position to the second position in response to at least one detection of a prescribed situation. At least one detector is provided for detecting a prescribed situation, the detector being for controlling the operation of the brake of the fan assembly, and the valve assembly, in response to the detecting.

FIELD OF THE INVENTION

This invention relates to controls for ventilation and exhaust ducts andfans and preferably, through not exclusively, relates to such anapparatus for use in offices, commercial kitchens, factories,warehouses, retail centres, production facilities, car parks, coolingtower fans, or the like.

BACKGROUND OF THE INVENTION

Exhaust apparatus for fumes and/or smoke are normally used in commercialkitchens, factories, production facilities, car parks, cooling towerfans or the like, to exhaust fumes and/or smoke and/or gasses caused bythe cooking or production process, or vehicle exhausts. Some exhaustsystems may have a hood above the stove or production facility, andducting to connect the hood to the outside atmosphere. One or more fansare built into the ducting or the hood to force the fumes and/or smokethrough the ducting. Filters may be used to remove the principalcontaminants from the fumes and/or smoke.

The fan or fans are normally controlled by a control panel. If a hood isused, it may be on the front of the hood. The fan may be multi-speedwith corresponding speed controls on the control panel. This means thefans may not be on when required, may be on when not required or may beoperated at a speed in excess of that required, or may be operated at aspeed less than that required. Such a situation can lead to ineffectiveor inefficient fume and/or smoke extraction, and/or excess use of thefan and therefore increased power consumption. Increased powerconsumption leads to increased energy costs. For example, in manycommercial kitchens exhaust fans are operated at full speed from thebeginning of food preparation until the last dish is cleaned. Also, incar parks they operate continually at full speed even when there is novehicle movement in operation. Such a level of use is very wasteful ofenergy and increases operational costs.

There have been proposed exhaust systems that monitor the ambienttemperature in the kitchen. Such systems do not operate in the presenceof noxious gasses or fumes, or when the carbon dioxide and/or carbonmonoxide level increases and the oxygen level decreases in the ambientair. Also, there is a tendency for the ducting to act as a conduit forfire if the premises are on fire, or for contaminants in the ducting tocatch fire. Ducting for exhaust systems does not normally deal with suchproblems and can enhance the fire by the fan(s) being on, and theducting being open to the outside atmosphere.

Also, ventilation systems for supplying air to zoned structures such asoffices, warehouses and retail centres rely on fire detectors adjacentthe zone boundary. At the zone boundary there are dampers in the duct.Upon the fire detector operating, the damper is operated to reduce therisk of fire spread. But by then the fire is close to penetrating theboundary. Also each damper operates independently and there is nostructured approach to use and operation of the dampers, and duct fans,for prevention of the spread of fire. Often the only source of air tofuel the fire is the ventilation duct. Therefore, closing the duct andbraking the fan to a complete stop as early as possible can slow thefire considerably by removing the source of oxygen.

SUMMARY OF THE INVENTION

In accordance with a first preferred aspect there is provided a fanassembly for placement in ducting of a ventilation or exhaust system foran environmental space, the fan assembly comprising:

-   -   (a) a motor having an output shaft;    -   (b) a fan mounted on the output shaft; and    -   (c) a brake for operation on the motor        wherein    -   (d) the brake is operable for stopping operation of the motor        upon a detection of a prescribed situation in one or more of:        the environmental space, and the ducting.

In accordance with a second preferred aspect there is provided a valveassembly for placement in ducting of a ventilation or exhaust system,the valve assembly comprising:

-   -   (a) a valve member for placement in the ducting for movement        between a first position where the ducting is substantially        open; and a second position where the valve member substantially        closes the exhaust ducting;    -   (b) the valve member being adapted to move from the first        position to the second position in response to at least        detection of a prescribed situation. The valve member may        mounted on a spindle for movement therewith between the first        and second positions; the spindle being for operative connection        to a drive motor for movement of the spindle for causing the        valve member to move between the first and second positions.

The prescribed situation may be the detecting of the presence of atleast one: heat, fire, smoke, fumes, gas, and obnoxious fumes. The gasmay be one or more of: a cooking gas, carbon monoxide, and carbondioxide.

The valve member may be sized and shaped to substantially accord to aninterior size and shape of the exhaust ducting.

In accordance with a third preferred aspect there is provided aventilation or exhaust system comprising:

-   -   (a) ducting;    -   (b) the fan assembly described above;    -   (c) the valve assembly described above; and    -   (d) at least one detector for detecting a prescribed situation        and for controlling the operation of:        -   (i) the brake of the fan assembly, and        -   (ii) the valve assembly            in response to the detecting.

The valve assembly may be located at, adjacent or near an outlet end ofthe ducting or at a boundary of zones of the environmental space. Theexhaust apparatus may further comprise a hood, the hood having a controlpanel. The control panel may comprise a reset control for resetting theat least one detector, releasing the brake of the fan assembly, andmoving the valve member to the first position. The exhaust apparatus mayfurther comprise at least one sensor for controlling the operation ofthe fan assembly. The at least one sensor may be at least one of a timesensor, a gas sensor, and at least one heat sensor. The at least onesensor may be arranged in groups. There may be a plurality of sensors, aplurality of groups, and a plurality of sensors in each group. Thenumber of sensors, or number of groups of sensors, activated maydetermine the speed of operation of the fan. For a time sensor, the timestage may determine the speed of operation of the fan.

In accordance with a fourth preferred aspect there is provided aventilation or exhaust system comprising:

-   -   (a) a fan assembly as described above; and    -   (b) a plurality of sensors for automatically controlling the        operation of the fan assembly by controlling the operational        speed of the fan assembly in accordance with the number,        location or nature of sensors that are activated.

The system may further comprise:

-   -   (c) a master on control for overriding the time sensor;    -   (d) a master off control for overriding the time sensor; and    -   (e) time controls for setting the first and second preset times.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the present invention may be fully understood and readilyput into practical effect, there shall now be described by way ofnon-limitative example only preferred embodiments of the presentinvention, the description being with reference to the accompanyingIllustrative drawings.

In the drawings:

FIG. 1 is a front perspective view of a preferred embodiment;

FIG. 2 is a vertical cross-sectional view of the embodiment of FIG. 1;

FIG. 3 is an enlarged view of one embodiment the fan assembly of FIG. 2;

FIG. 4 is block diagram of an alternative embodiment for the fanassembly;

FIG. 5 is an enlarged view of the duct valve of FIG. 2 when in the openposition;

FIG. 6 is an enlarged view of the duct valve of FIG. 2 in the closedposition;

FIG. 7 is a vertical cross-sectional view of an alternative duct valuein the open position;

FIG. 8 is a view corresponding to FIG. 7 in the closed position;

FIG. 9 is an enlarged view of the part of the stove and hood of FIG. 2illustrating the sensor arrangement;

FIG. 10 is a block diagram of a first sensor array;

FIG. 11 is a flow chart for the operation of the embodiment of FIG. 10;

FIG. 12 is a flow chart for the operation of the embodiment of FIG. 10with timing sensors, and

FIG. 13 is an illustration of a zone system for fire and other control.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

To refer to FIGS. 1 and 2, there is illustrated a commercial stove 10with an exhaust hood 12. Ducting 14 connects the exhaust hood 12 to theoutside atmosphere 16. Although a stove 10 is shown, it could be anycommercial or industrial equipment that produces or uses smoke and/orfumes and/or noxious gasses, a car park for removing vehicle exhaustfumes, and so forth.

The stove 10 has hobs 18 for use in the cooking of food, and are or moreovens 20 also used in the cooking of food.

The exhaust hood 12 has a control panel 22 for controlling the operationof the exhaust hood 12, including the operation of a fan assembly 24.Although a single fan assembly 24 is shown, there may be two or more fanassemblies. The fan assembly 24 may be of any suitable form or nature.Preferably, the fan assembly 24 is multiple speed.

Also in ducting 14 is a valve 26 that is shown in the open position inFIG. 2, and which is adjacent the outlet end 28 of the ducting 14. Theoutlet end 28 is in the outside and is therefore outside the premises inwhich stove 10, hood 12 and ducting 14 are located. The outlet end 28may have a weather cap 30, if required or desired. Valve 26 may be atany location in ducting 14. There may be more than one valve 26 inducting 14. If ducting 14 is zones, there may be a valve 26 for eachzone.

One form of the fan assembly 24 is shown in more detail in FIG. 3. Thefan assembly 24 may have a shroud 32. The shroud 32 may be spaced fromducting 14, or may be a relatively sealing fit in ducting 14.Non-rotatably mounted within shroud 32 is a drive motor 34 with anoutput shaft 36. Mounted on output shaft 36 is a fan 38. Motor 34 andfan may be within the shroud 32. Motor 34 is powered by an electricsupply cable 40 for rotating shaft 36 and thus fan 38.

Mounted for acting on shaft 36 is a brake 42. Brake 42 is secured to themotor 34 and/or shroud 32 so that it does not rotate relative thereto.Shaft 42 rotates relative to brake 42.

When a prescribed situation such as, for examples, smoke, fumes or heatabove a preset density or level is detected in ducting 14 by one or moreof smoke, fume or heat detectors 44, 46, and if the motor 34 is on, themotor 34 is immediately switched off and brake 42 applied so that themotor 34 and shaft 36, and thus fan 38, will stop rotating in theshortest possible time. This prevents or stops air flow in ducting 14due to fan assembly 24. Furthermore, as the air is moving in ducting 14the air will have momentum. By use of the brake 42, the fan 38 is heldstationary. As such, the fan 38 becomes a damper on the movements of airwithin ducting 14 and this air movement ceases far more speedily ifbrake 42 is not applied, the shaft 36 and thus fan 38 would continue torotate at a decreasing rate, the rate of decrease depending on functionwithin motor 34, the inertia of the fan 38 and the momentum of the airflow in ducting 14 over fan assembly 24. Further, by use of brake 42 thegeneration of a back EMF by motor 34 is minimized.

The motor 34 and brake 42 are operatively connected to detectors 44, 46by a wiring loom 48. The detectors 44, 46 may have the same, ordifferent, preset smoke, fume or heat density or other levels. The motor34 and brake 42 may also be connected to a fire alarm system, so thatupon the fire alarm being activated, motor 34 is switched off and brake42 applied.

An alternative is shown in FIG. 4 where in place of the physical brake42 there is a variable speed drive 43 for the motor 34 to enable motor34 to have a number of speeds of operation. The variable speed drive 34includes an electric brake component that operates electrically to stopmotor 34. The variable speed drive 43 may be at the motor 34, or may beremote from the motor 34.

Also operatively connected to smoke fume or heat detectors 44, 46 bycable loom 48 is a duct valve 26 located in the ducting 14. The valve 26may be anywhere in the ducting 14. As shown, it is at, adjacent or nearthe outer end 28 of ducting 14. There may be more than one valve 26 inducting 14. If ducting 14 is in zones, there may be a valve 26 for eachzone, preferably at the boundary of each zone.

The valve 26 is shown in the open position in FIGS. 2 and 5, and in theclosed position in FIG. 6. Upon either or both of the smoke detectors44, 46 operating as described above, a step motor 50 operates to rotatea spindle 52 by 90° so that a valve member 54 is also rotated by 90°from the open position (FIGS. 2 and 5) to the dosed position (FIG. 6).Valve member 54 is mounted on spindle 52 to rotate therewith. The valvemember 54 may almost, or substantially, seal the ducting 14 to createstatic pressure within the ducting 14, and thus to prevent the passageto the outlet end 28 of smoke, fumes or the like. By having the valvemember at, adjacent or near the outlet end 28, any smoke, fumes or thelike generated anywhere in ducting 14 will be prevented from passingthrough outlet end 28.

The valve member 54 will be sized and shaped to substantially accord tothe internal size and shape of the ducting 14. Thus, if ducting 14 is ofa circular cross-sectional shape, the valve member 54 will be circular(as shown) and of substantially the same radius. If the ducting 14 is ofa square cross-sectional shape, the valve member 54 will also be squareand of substantially the same side length.

In this way, upon an excessive level of smoke or fumes in ducting 14being detected by either or both detectors 44, 46, valve 26 operates toclose the outlet end 28 of the ducting 14; and motor 34 is switched offand brake 42 or 43 applied to prevent rotation of fan 38. This prevents,or minimizes, movement of the smoke or fumes within the ducting 14, andcan prevent contamination of the outside atmosphere 16 if the smoke orfumes are of a polluting or toxic nature.

As shown in FIG. 13, there may be two ducts 14 and 214 for supplying orexhausting air to or from outlets 80 and 280 in a zone 82 of a building.Air supply may be conditioned air. The zone 82 is defined by zoneboundary walls 84. Duct valves 86 and 286 are located in ducts 14, 214respectively. A number of sensors and detectors 44 are located in zone82 and/or ducts 14, 214 for detecting a prescribed situation in zone 82and/or ducts 14, 214. The prescribed situation may be the presence ofone or more of: smoke, fumes, gas, heat, noxious fumes, and fire. Thegas may be of any form including a cooking gas, carbon dioxide and acarbon monoxide. Valves 14, 214 operate as described above if any one ofthe sensors or detectors 44 is activated. This isolates zone 82 as earlyas possible so that any fire in zone 82 is starved of oxygen and willthus spread at a slower rate. Similarly, valves 86, 286 may also belinked to and operated by the building fire alarm to prevent the spreadof smoke or fumes even if the prescribed situation is not in zone 82.

The control panel 22 may include a ‘reset’ button or switch 56 ifrequired or desired to enable the valve 26 to return to the openposition (FIGS. 2 and 4), for brake 42 to be released and motor 34switched on, and for resetting the detectors 44, 46.

FIGS. 7 and 8 show an alternative form of valve 26. Here, the valvemember 55 comprises a number of portions 57 hingedly connected togetherand being biased to the closed position. A stop 59 holds them in theopen position against the bias. An electromagnetic motor 51 is used torelease the stop 59 to close the duct 14, and to subsequently reopen theduct 14.

In FIGS. 9 and 10, there is shown a number of possible sensorarrangement for enabling the automatic operative of the fan assembly 24.

In FIG. 9, there are three possible sensors 58, 60, 62 operativelyconnected to fan assembly 24 by wiring loom 48 and control box 68 thatcontains all necessary control functionality (including relays, and soforth) for the valve assembly 26, fan assembly 24, control panel 22, andthe sensors/detectors 44, 46, 58 60 and 62.

Sensor 58 is one or more sensors for heat or temperature, but preferablyheat, and located at, on or adjacent hobs 18 so that upon one or more ofthe hobs 18 being operated to generate heat for cooking, the sensor 58will operate to switch on fan assembly 24. Upon the heat ceasing, sensor58 will operate to switch off the fan assembly 24. This may causerepeated, short cycles of operation. As the largest consumption ofelectricity by fan assembly 24 is at start-up, although this system iseffective it may not be electrically efficient. However, this may beapplicable for car parks where a combination of heat from engines andexhausts or exhaust fumes may be detected. Also, or alternatively, atime-based system may be utilized to cover peak operational periods.

Sensor 60 is somewhat similar to sensor(s) 58 but is located in the hood12 so that it detects heat from hobs 18. This may reduce the number ofsensors required, but may suffer the same problem.

Sensor 62 is a time sensor. With commercial kitchens, and manyindustrial processors, the period of peak operation is known. Forexample, a restaurant that is open for lunch from midday to 3 pm willhave the kitchen preparing foods by cooking from about 11.00 am, andwill be cooking until about 2.00 pm. Therefore, the fan assembly 24needs to operate from 11.00 am to 2.00 pm only. Therefore, time sensor60 will automatically switch on the fan assembly 24 at 11.00 am, andautomatically switch if off at 2.00 pm. The control panel 22 may containtime adjusting knobs 64 for adjusting the on and off times. Within thetime period 11.00 am to 2.00 pm, the operating speed of the fan assembly24 may vary. As shown in FIG. 12, at the beginning of operation the fan28 may be at a first preset speed in the range 25% to 75%, preferably50%; at a second stage in the timing at a second preset speed in therange 75% to 100%, preferably 80%; and at a third stage at a third speedbeing full speed.

A further sensor 74 may be provided for sensing a prescribed situationin the interior or environmental space (such as zone 82). The prescribedsituation may be the presence of one or more of: smoke, fumes, gas,heat, noxious fumes, and fire. The gas may be of any form including acooking gas, carbon dioxide and a carbon monoxide.

The control panel 22 may also have a master on switch 66 for manuallyswitching on the fan assembly 24 irrespective of the time ortemperature, and a master off switch 66 for manually switching off thefan assembly 24 irrespective of the time or temperature.

Two or more of the sensors 58, 60, 62 may be provided and may beconnected in series so that the fan assembly 24 will only, operate whenall the sensors are active; or in parallel so that the fan assembly willoperate when any one or more of the sensors is active.

FIG. 10 shows multiple sensors 58 on hobs 18, each hob having a potsupport 64. Here the smallest hob 66 has one sensor 58; the small,intermediate hob 68 has two sensors; the two larger, intermediate hob 70has two sensors 58; and the largest hob 72 has four sensors 58. However,each hob 66, 68, 70 and 72 may have the same number of sensors 58, ifrequired.

As is shown in FIG. 11, the fan 28 is preset to start at a predeterminedspeed when first operational. That may be in the range of 25% to 75%,preferably 50%. When a sensor 58 is activated it determines if one ormore sensors 58 have been activated. The sensors 58 may be arranged ingroups, if desired. If one sensor 58, or one group of sensors 58, isactivated, the fan speed is increased to a second predetermined speedthat may be in the range 60% to 80%, preferably 70%. If a second sensor58, or a second group of sensors 58, is activated the fan speed isincreased to a third predetermined speed in the range 75% to 95%,preferably 85%. If all sensors 58, or all groups of sensors 58, areactivated, the fan 28 is increased to full speed. The three-speedoperation may be two-speed, four-speed, five-speed, or a continuousspeed, if required or desired.

In this way the operation of the fan assembly 24 can be controlled in anautomatic manner based on the number, nature and location of sensorsactivates to thus reduce electricity consumption, but still allowingmanual override if required or desired. This is applicable in commercialkitchens, car parks, cooling tower fans, production facilities,factories, warehouses, retail centres, offices, or the like.

Whilst there has been described in the foregoing description preferredembodiments of the present invention, it will be understood by thoseskilled in the technology concerned that many variations ormodifications in details of design or construction may be made withoutdeparting from the present invention.

1-41. (canceled)
 42. A ventilation or exhaust apparatus comprising: afan assembly comprising a motor having an output shaft, and a fanmounted on the output shaft; and a plurality of detectors forautomatically controlling the operation of the fan assembly bycontrolling the operational speed of the fan assembly in accordance withthe number, location or nature of the detectors that are activated. 43.A ventilation or exhaust apparatus as claimed in claim 42, wherein themotor and fan are within a shroud.
 44. A ventilation or exhaustapparatus as claimed in claim 42, wherein the motor is a variable speeddrive motor.
 45. A ventilation or exhaust apparatus as claimed in claim42, wherein the plurality of detectors comprises at least two detectorsselected from a group consisting of a time sensor, a heat sensor, atemperature sensor, a gas sensor, and a fumes sensor.
 46. A ventilationor exhaust apparatus as claimed in claim 45, wherein the plurality ofdetectors is arranged in groups.
 47. A ventilation or exhaust apparatusas claimed in claim 45, wherein a number of detectors activateddetermines the fan assembly operational speed.
 48. A ventilation orexhaust apparatus as claimed in claim 45, wherein a stage in a timesensor determines the fan assembly operational speed.
 49. A ventilationor exhaust apparatus as claimed in claim 42, further comprising: a valveassembly for placement in ducting of a ventilation or exhaust system,the valve assembly comprising: a valve member for placement in theducting for movement between a first position where the ducting issubstantially open, and a second position where the ducting issubstantially closed; the valve member being adapted to move from thefirst position to the second position to at least one detection of aprescribed situation; and the valve assembly being located at, adjacentor near an outlet end of the ducting.
 50. A ventilation or exhaustapparatus as claimed in claim 49, wherein the valve member is sized andshaped to substantially close off an interior of the ducting.
 51. Aventilation or exhaust apparatus as claimed in claim 49, wherein theprescribed situation may be the presence of one or more of smoke, fumes,gas, heat, noxious fumes, and fire, and the gas includes at least one ofa cooking gas, carbon dioxide or carbon monoxide.
 52. A ventilation orexhaust apparatus as claimed in claim 49 wherein the plurality ofdetectors comprises at least two detectors selected from a groupconsisting of a time sensor, a heat sensor, a temperature sensor, a gassensor, and a fumes sensor.
 53. A ventilation or exhaust apparatus asclaimed in claim 52, wherein the plurality of detectors is arranged ingroups.
 54. A ventilation or exhaust apparatus as claimed in claim 53,wherein a number of detectors activated determines the fan assemblyoperational speed.
 55. A ventilation or exhaust apparatus as claimed inclaim 53, wherein a stage in a time detector determines the fan assemblyoperational speed.
 56. A fan assembly for placement in ducting of aventilation or exhaust system for an environment space, the fan assemblycomprising: a motor having an output shaft; a fan mounted on the outputshaft; and a brake mounted for operation on the motor; wherein the brakeis operable for stopping rotation of the motor output shaft upon adetection of a prescribed situation by at least one detector in one ormore of the environmental space and the ducting.
 57. A fan assembly asclaimed in claim 56, wherein the motor and fan are within a shroud. 58.A fan assembly as claimed in claim 56, wherein the motor is a variablespeed drive motor and the brake comprises an electric brake component ofthe variable speed drive motor.
 59. A fan assembly as claimed in claim56, wherein the prescribed situation is the presence of one or more ofsmoke, fumes, gas, heat, noxious fumes and fire; and the gas includes atleast one of a cooking gas, carbon dioxide or carbon monoxide.
 60. A fanassembly as claimed in claim 56, wherein the at least one detectorcomprises at least one detector selected from a group consisting of atime sensor, a heat sensor, a temperature sensor, a gas sensor, and afumes sensor.
 61. A fan assembly as claimed in claim 56, wherein aplurality of sensors is arranged in groups.
 62. A fan assembly asclaimed in claim 56, wherein a number of sensors activated determinesthe fan assembly operational speed.
 63. A fan assembly as claimed inclaim 56, wherein a stage in a time sensor determines the fan assemblyoperational speed.
 64. A fan assembly as claimed in claim 56, furthercomprising: a plurality of detectors for automatically controlling theoperation of the fan assembly by controlling the operational speed ofthe fan assembly in accordance with the number, location or nature ofthe detectors that are activated.
 65. A fan assembly as claimed in claim56, further comprising: noxious fumes and fire; and the gas includes atleast one of a cooking gas, carbon dioxide or carbon monoxide.
 60. A fanassembly as claimed in claim 56, wherein the at least one detectorcomprises at least one detector selected from a group consisting of atime sensor, a heat sensor, a temperature sensor, a gas sensor, and afumes sensor.
 61. A fan assembly as claimed in claim 60, wherein aplurality of sensors is arranged in groups.
 62. A fan assembly asclaimed in claim 60, wherein a number of sensors activated determinesthe fan assembly operational speed.
 63. A fan assembly as claimed inclaim 60, wherein a stage in a time sensor determines the fan assemblyoperational speed.
 64. A fan assembly as claimed in claim 56, furthercomprising: a plurality of detectors for automatically controlling theoperation of the fan assembly by controlling the operational speed ofthe fan assembly in accordance with the number, location or nature ofthe detectors that are activated.
 65. A fan assembly as claimed in claim56, further comprising: a valve assembly for placement in ducting of aventilation or exhaust system, the valve assembly comprising: a valvemember for placement in the ducting for movement between a firstposition where the ducting is substantially open, and a second positionwhere the ducting is substantially closed; the valve member beingadapted to move from the first position to the second position to atleast one detection of a prescribed situation; and the valve assemblybeing located at, adjacent or near an outlet end of the ducting.
 66. Afan assembly as claimed in claim 65, wherein the valve member is sizedand shaped to substantially close off an interior of the ducting.
 67. Afan assembly as claimed in claim 65, wherein the prescribed situationmay be the presence of one or more of smoke, fumes, gas, heat, noxiousfumes, and fire, and the gas includes at least one of a cooking gas,carbon dioxide or carbon monoxide.
 68. A fan assembly as claimed inclaim 65, further comprising: the at least one detector comprises atleast one detector selected from a group consisting of a time sensor, aheat sensor, a temperature sensor, a gas sensor, and a fumes sensor. 69.A fan assembly as claimed in claim 68, wherein a plurality of detectorsis arranged in groups.
 70. A fan assembly as claimed in claim 68,wherein a number of detectors activated determines the fan assemblyoperational speed.
 71. A fan assembly as claimed in claim 68, wherein astage in a time detector determines the fan assembly operational speed.72. A fan assembly as claimed in claim 65, wherein the at least onedetector comprises: a plurality of detectors for automaticallycontrolling the operation of the fan assembly by controlling theoperational speed of the fan assembly in accordance with the number,location or nature of the detectors that are activated.
 73. A valveassembly for placement in ducting of a ventilation or exhaust system,the valve assembly comprising: a valve member for placement in theducting for movement between a first position where the ducting issubstantially open, and a second position where the ducting issubstantially closed; the valve member being adapted to move from thefirst position to the second position in response to the detection of atleast one or more of smoke, fumes, gas, heat, noxious fumes and fire;and the gas includes at least one of a cooking gas, carbon dioxide orcarbon monoxide; the valve member being for location at, adjacent ornear an outlet end of the ducting.
 74. A valve assembly as claimed inclaim 73, wherein the valve member is sized and shaped to substantiallyclose off an interior of the ducting.
 75. A valve assembly as claimed inclaim 73, further comprising: a detector for detecting the presence ofone or more of: smoke, fumes, gas, heat and noxious fumes; and a controlpanel comprising a reset control for resetting the detector, and movingthe valve member to the first position.
 76. A valve assembly as definedin claim 75, wherein the detector comprises at least two detectorsselected from the group consisting of a sensor, a heat sensor, atemperature sensor, a gas sensor, and a fumes sensor.
 77. A valveassembly as defined in claim 76, further comprising at least one of: amaster on control for overriding a time sensor; a master off control foroverriding a time sensor; and time controls for setting a plurality ofpreset times for the operation of the time sensor.